It was said to the men of old,
"You shall not swear falsely, but shall perform to the Lord what you have
sworn."253

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The eighth commandment forbids misrepresenting the truth in our relations with
others. This moral prescription flows from the vocation of the holy people to
bear witness to their God who is the truth and wills the truth. Offenses
against the truth express by word or deed a refusal to commit oneself to moral
uprightness: they are fundamental infidelities to God and, in this sense, they
undermine the foundations of the covenant.